[PATCH v2 15/22] thermal: intel: hfi: Define a default class for unclassified tasks

[Ricardo Neri]

A task may be unclassified if it has been recently created, spend most of
its lifetime sleeping, or hardware has not provided a classification.

Most tasks will be eventually classified as scheduler's IPC class 1
(HFI class 0). This class corresponds to the capabilities in the legacy,
classless, HFI table.

IPC class 1 is a reasonable choice until hardware provides an actual
classification. Meanwhile, the scheduler will place other tasks with higher
scores on higher-performance CPUs.

Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Len Brown <len.brown@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Tim C. Chen <tim.c.chen@xxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
---
Changes since v1:
 * Now the default class is 1.
---
 drivers/thermal/intel/intel_hfi.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/intel/intel_hfi.c b/drivers/thermal/intel/intel_hfi.c
index 1f7b18198bd4..1b3fd704ae9a 100644
--- a/drivers/thermal/intel/intel_hfi.c
+++ b/drivers/thermal/intel/intel_hfi.c
@@ -187,6 +187,19 @@ static struct workqueue_struct *hfi_updates_wq;
 #ifdef CONFIG_IPC_CLASSES
 static int __percpu *hfi_ipcc_scores;
 
+/*
+ * A task may be unclassified if it has been recently created, spend most of
+ * its lifetime sleeping, or hardware has not provided a classification.
+ *
+ * Most tasks will be classified as scheduler's IPC class 1 (HFI class 0)
+ * eventually. Meanwhile, the scheduler will place tasks of higher IPC score
+ * on higher-performance CPUs.
+ *
+ * IPC class 1 is a reasonable choice. It matches the performance capability
+ * of the legacy, classless, HFI table.
+ */
+#define HFI_UNCLASSIFIED_DEFAULT 1
+
 int intel_hfi_has_ipc_classes(void)
 {
 	return cpu_feature_enabled(X86_FEATURE_ITD);
@@ -222,7 +235,7 @@ int intel_hfi_get_ipcc_score(unsigned short ipcc, int cpu)
 		return -EINVAL;
 
 	if (ipcc == IPC_CLASS_UNCLASSIFIED)
-		return -EINVAL;
+		ipcc = HFI_UNCLASSIFIED_DEFAULT;
 
 	/*
 	 * Scheduler IPC classes start at 1. HFI classes start at 0.
-- 
2.25.1